The invention relates to a piston for charging and discharging fluid in a fluid chamber. In a preferred embodiment of the invention, the piston is used in a high pressure, high temperature environment, (HPHT) specifically HPHT press apparatuses. For example, such presses are useful in the superhard materials production industry. Some examples of superhard materials that high pressure, high temperature presses sinter includes: cemented ceramics, diamond, polycrystalline diamond, and cubic boron nitride. HPHT press apparatuses typically require significant structural mass to withstand the ultra high pressures essential to synthetically form superhard materials.
U.S. Pat. No. 7,231,766 to Hall et al., which is herein incorporated by reference for all that it contains, discloses a piston valve for charging and discharging a first fluid chamber. The piston valve includes a piston shaft and a ring comprising a seal element. The piston shaft has a first end and a second end with the first end including a counter bore having at least one vent. The ring is disposed within a cylinder and the seal element is disposed intermediate the piston shaft and the ring. The piston valve may be used for intensification purposes such as in a high pressure high temperature hydraulic cartridge.